Correctional facilities have traditionally recorded telephone conversations of its inmates. Such recordings may be conducted pursuant to a variety of rules that range anywhere from only recording conversations of calls made to specific telephone numbers, calls made by specific inmates or made using specific telephones, to recording every single call. Various techniques for recording telephone calls are known. Examples of known recording techniques include those described in U.S. Pat. No. 6,647,096 titled “SYSTEM AND METHOD FOR REMOTELY CONTROLLING AUTOMATED CALL PLACEMENT CALL MONITORING FUNCTIONS,” U.S. Pat. No. 6,665,376 titled “SELECTIVELY ACTIVATED INTEGRATED REAL-TIME RECORDING OF TELEPHONE CONVERSATIONS WITH AUTOMATED DOCUMENTATION OF CONSENT TO CALL RECORDING,” and those described in U.S. Pat. No. 7,058,163 titled “SYSTEM AND METHOD FOR EX POST FACTO PRESERVING A RECORDED CONVERSATION”, the disclosures of which are hereby incorporated herein by reference.
Some audio recordings are made on wire susceptible to magnetization or on magnetic tape. Audio recordings are also made by passing the audio through an analog-to-digital converter (ADC) and by storing digital data in a digital storage medium such as a magnetic hard disk, a semiconductor memory, or optical or magneto-optical storage such as a writable CD-ROM. Further, in certain instances, the audio is communicated in digital form over a communication network (e.g., as with Voice over IP (VOIP)), wherein the digital audio may be captured and stored to a digital storage medium.
Thus, recording of inmate telephone calls is well known. Such recordings may be monitored by appropriate authorities to detect information regarding the security of facilities, continuing or past criminal activity, etc. Monitoring of the recordings may be performed manually (e.g., by a person listening to the recording) and/or may be performed robotically (or autonomously) by, for example, computer processing logic for analyzing the recordings for certain keywords, etc. In some instances, the recordings may be stored for later use, such as for later investigations, later used as evidence in a court of law, etc.
For many uses, such as when being used as evidence in a court of law, it is desirable to establish the authenticity of recorded calls. Common practices for establishing authenticity and preserving a “chain of custody” of tangible evidence (e.g. a weapon, item of clothing, collected body fluid, etc.) are well known. In general, each step of handling the tangible evidence from collection of the evidence to the proffer of evidence in a courtroom must be attested to by a witness, typically a police officer, a detective, a crime scene investigator, or a laboratory technician. When the evidence is not being actively handled by anyone, it is typically placed in a sealed physical container and stored to an evidence storage facility (e.g., evidence locker). The physical container is typically initialed, dated, and secured in a fashion that is intended to show that no tampering of the evidence took place during its storage.
When desiring to proffer recordings of telephone calls as evidence, the issue of authentication must be addressed, as with traditional tangible evidence. Establishing the authenticity of a recording of a telephone call presents certain difficulties not present for establishing the authenticity of tangible evidence. It is well known that analog recordings and digital data files are readily modified in ways that may be very difficult to detect afterwards. For example, recordings are typically stored to a file having a standard audio file format, such as a WAV or an AU audio file format. These file formats are so well known that it raises an increased risk of a user editing a recording in some way, and within the file format there is nothing to prove the authenticity of the audio (i.e., to prove that the audio has not been altered). Some of the file formats contain additional information in headers to further identify what the content of the file is, but there is nothing to prevent the editing of this header information or to prove that the header information has not been modified.
When the authenticity is put into question, it may be desirable to prove that a recording of a telephone call has not been tampered with or altered, and that it thus accurately reflects the audio of the telephone call. Such a desire may arise in a variety of contexts and for a variety of recorded calls, such as with financial transactions conducted via telephone, conversations of inmates of correctional facilities conducted via telephone, governmental wiretaps, etc.